The presence of the disease sickle cell anemia illustrates that natural selection does not always eliminate _________ alleles.
A. polymorphic
B. dominant
C. neutral
D. recessive
D. recessive
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The cell walls of fungi are composed of:
a. cellulose. b. lipids. c. glycogen. d. chitin. e. chlorophyll
When two frog species, Rana pippins and Rana sylvatica, mate, the offspring die early in embryonic development. This is an example of ___________.
A. Hybrid sterility B. Reduced hybrid fertility C. Mechanical isolation D. Reduced hybrid viability
Small structure in a cell that performs a specific function is the ___________.
Fill in the blank(s) with the appropriate word(s).
An operon is
a. a gene cluster transcribed as a single mRNA. b. an enzyme responsible for turning genes on and off. c. a site where DNA replication begins. d. a segment of DNA that can move.